This invention relates to a chopper control device utilizing a magnetic phase shifter and more particularly to a chopper control device of the kind above described which is capable of limiting the phase angle of the output of the magnetic phase shifter depending on the intensity of an external magnetic field applied thereto.
A magnetic amplifier can singly carry out various operations including comparison, amplification, wave shaping and time constant regulation of various signals and can operate without being substantially adversely affected by external noises. Thus, a magnetic amplifier is suitable for use as a means for controlling a chopper which controls the on-off state of a large current. A thyristor chopper control device is commonly known in which such magnetic amplifier is used as a phase controller or magnetic phase shifter. A pair of magnetic phase shifters have been generally required hitherto for the purpose of notch setting control, for example, for electric motors used in electric cars. However, the magnetic phase shifters are quite expensive and the circuit including one pair of such magnetic phase shifters is quite complex in circuitry tending to give rise to reductions of reliability.